The present invention provides a magnetic tape device (a tape drive), method, and program for writing and reading multiple records including video data to/from a tape medium (tape, medium). More particularly, the present invention relates to reading video data saved on a tape included in a tape drive and enabling a video application to reproduce video with few interruptions.
Linear Tape File System (LTFS) is a file system that can handle data on a tape in file format. One application of the LTFS is saving video data on a tape and reading video data directly from the tape for playback. A problem associated with this technique is failure to read data due to some trouble when reading data from the tape.
Tape drives compliant to the LTO standard and having a large capacity (IBM TS series) ensure data integrity in terms of bits. There are features available for checking data integrity during reading/writing of a drive, and a mechanism has been adopted that inhibits data from being sent from the drive to a host when written data is different from read data even in one bit. When error checking on data read from the tape fails, the data is not sent to the host. An error recovery procedure (ERP) for error recovery is carried out and attempts are repeated until error checking is passed. When checking ends in a failure, then an error results.
While data is often successfully read from tape with an ERP, when an ERP occurs in the case of direct reproduction of video data, the reproduction of video data is interrupted during execution of the ERP. Also, when an error cannot be recovered by execution of an ERP, reproduction of video data stops.
For a certain type of data such as video data, usages that do not necessarily require bit-wise guarantee are conceivable. Some troubles are acceptable to users such as noise in an image transmitted via an artificial satellite that can be seen on a typical television. For certain usages, quick reproduction of the entire video data is desired rather than high-resolution reproduction of video, and for such applications, there is a greater demand for elimination of interruption or stop of an image than elimination of noise in or skips of an image. However, tape drives supported by the current LTFS do not allow for such a usage.
JP2010-225196A discloses a technique for skipping a portion of read data where an error has occurred, transferring only valid data to a host, in which the read data is then sent to an application with dummy data embedded in the skipped portion.
However, JP2010-225196A does not contemplate writing data such that the beginning of a data set is aligned with the beginning of a record and sending the entire video data without discontinuities and with minimum frame drops.